"It's just that sometimes a man wants to be let off the lash."
"I wouldn't recommend it." He frowned at him. "Don't scratch your hood."
"My scalp itches. Us jews are not supposed to lose our hair."

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First, I think "lash" is a typo for "leash," which makes much more sense.

As for hood, I don't think it refers to a skull cap (or yarmulke), and my impression is that the man is wearing a hoodie (a sweatshirt with a hood) and is scratching his head through the fabric of the hood. He is apparently losing his hair and it itches.